U.S. patent application number 10/868502 was filed with the patent office on 2005-03-31 for keypad in textiles with capacitive read-out circuit.
This patent application is currently assigned to Infineon Technologies AG. Invention is credited to Jung, Stefan, Lauterbach, Christl.
Application Number | 20050069695 10/868502 |
Document ID | / |
Family ID | 26010782 |
Filed Date | 2005-03-31 |
United States Patent
Application |
20050069695 |
Kind Code |
A1 |
Jung, Stefan ; et
al. |
March 31, 2005 |
Keypad in textiles with capacitive read-out circuit
Abstract
Input apparatus including at least one textile fabric carrier,
at least one flexible, wire- and/or thread-like electrical
conductor comprising at least one weft and/or warp thread of the
fabric carrier, and at least one electrically conductive, flexible
key device which is electrically connected to a key connection of
the conductor, wherein the conductor is designed for the connection
of an evaluation device.
Inventors: |
Jung, Stefan; (Munich,
DE) ; Lauterbach, Christl;
(Hohenkirchen-Siegertsbrunn, DE) |
Correspondence
Address: |
DARBY & DARBY P.C.
P. O. BOX 5257
NEW YORK
NY
10150-5257
US
|
Assignee: |
Infineon Technologies AG
Munich
DE
81669
|
Family ID: |
26010782 |
Appl. No.: |
10/868502 |
Filed: |
June 14, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10868502 |
Jun 14, 2004 |
|
|
|
PCT/EP02/13748 |
Dec 4, 2002 |
|
|
|
Current U.S.
Class: |
428/328 |
Current CPC
Class: |
D03D 15/593 20210101;
H03K 2217/960755 20130101; H01H 2239/006 20130101; D03D 1/0088
20130101; D10B 2401/16 20130101; H01H 2203/0085 20130101; H03K
2017/9602 20130101; H03K 17/9622 20130101; D03D 15/00 20130101;
Y10T 428/256 20150115; D10B 2101/20 20130101 |
Class at
Publication: |
428/328 |
International
Class: |
B32B 005/16 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 14, 2001 |
DE |
101 61 598.1 |
May 8, 2002 |
DE |
102 20 642.2 |
Claims
1. An input apparatus comprising: at least one textile fabric
carrier; at least one flexible, wire-like and/or thread-like
electrical conductor comprising at least one weft and/or warp
thread of the fabric carrier; and at least one electrically
conductive, flexible key device which is electrically connected to
a key connection of the conductor; wherein the conductor is
designed for the connection of an evaluation device.
2. The input apparatus as claimed in claim 1, wherein the key
device comprises a conductive silicone adhesive.
3. The input apparatus as claimed in claim 1, wherein the key
device has a key layer whose thickness is small relative to its
dimensions in the layer plane and which is areally fixed to the
fabric carrier.
4. The input apparatus as claimed in claim 1, wherein the conductor
has an electrical insulation, which is locally removed for
electrical connection to the key device.
5. The input apparatus as claimed in claim 1, further comprising a
plurality of key devices arranged in particular linearly or in
matrix-like fashion.
6. The input apparatus as claimed in claim 5, wherein the
conductors are electrically connected to the key devices in each
case being electrically connected at crossover points to contact
redistribution conductors which run essentially perpendicularly
thereto and in each case comprise at least one electrically
conductive weft or warp thread of the fabric carrier.
7. The input apparatus as claimed in claim 6, wherein the contact
redistribution conductor are arranged in a manner spaced apart
uniformly from one another in the fabric carrier.
8. The input apparatus as claimed in claim 1, further comprising an
evaluation device for detecting an actuation of at least one of the
key devices.
9. The input apparatus as claimed in claim 8, wherein a first group
of key devices is designed as reference key devices and a second
group of key devices is designed as input key devices.
10. The input apparatus as claimed in claim 9, wherein the
evaluation device is designed for evaluating electrical potential
difference or electrical resistance between one of the input key
devices and at least one of the reference key devices.
11. The input apparatus as claimed in claim 9, wherein the input
key devices are connected, by a conductor arranged in the fabric
carrier, serially and with high impedance to an input connection of
the evaluation device and the reference key devices are connected
with low impedance to a reference connection of the evaluation
device.
12. The input apparatus as claimed in claim 11, wherein the
evaluation device is designed for detecting an actuation of one of
the input key devices by evaluation of the electrical resistance
between the input and reference connections.
13. The input apparatus as claimed in claim 8, wherein the
evaluation device is designed for outputting a control signal if it
detects an actuation of at least two of the key devices in a
predetermined temporal sequence.
14. The input apparatus as claimed in claim 8, wherein the
evaluation device is designed for capacitively detecting an
actuation of at least one of the key devices.
15. The input apparatus as claimed in claim 14, further comprising
an electrical shielding device, which is designed for electrically
shielding at least one of the key devices from a side of the
textile fabric carrier.
16. The input apparatus as claimed in claim 15, wherein the
shielding device is a thin conductive layer arranged spaced apart
from and running essentially parallel to the at least one of the
key devices.
17. A method for producing an input apparatus comprising the steps
of: providing a textile fabric carrier having at least one
flexible, wire-like and/or thread-like electrical conductor
comprising at least one weft and/or warp thread of the fabric
carrier; electrically connecting an electrically conductive,
flexible key device to a key connection of the conductor; and
connecting an evaluation device to the conductor.
18. The method as claimed in claim 17, wherein the key device is
fitted using a screen printing method.
19. The method as claimed in claim 17, wherein an electrical
insulation of the conductor is locally removed before the step of
electrically connecting the key device.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of International Patent
Application Ser. No. PCT/EP02/13748, filed Dec. 4, 2002, which
published in German on Jun. 26, 2003 as WO 03/052541, and is
incorporated herein by reference in its entirety.
FIELD OF THE INVENTION
[0002] The invention relates to an input apparatus and to a method
for producing an input apparatus.
BACKGROUND OF THE INVENTION
[0003] The integration of electronic components in textile consumer
items, such as e.g. items of clothing, requires not only the
implementation of the electronic circuits but also the
implementation of an apparatus for data inputting, in particular a
tactile user interface. Despite ever more sophisticated
possibilities of voice control systems, key inputting is still
necessary or desirable in many applications since, on the one hand,
voice control systems can only be used to a limited extent in many
situations and, on the other hand, key inputs can often be carried
out more reliably, more simply and more rapidly. By way of example,
a continuously variable volume control cannot be realized in a
convenient manner by means of voice control systems.
[0004] Known attempts to integrate keyboards or input apparatuses
into a textile environment comprise, in particular, incorporating
or sewing conventional flexible keyboards into a textile fabric
carrier. Furthermore, multilayer material fabric structures are
known in which, by means of mechanical actuation, an electrical
contact or proximity can be produced in the multilayer construction
and read resistively or capacitively. Finally, keyboards whose keys
and leads have been embroidered on or sewn on from conductive and
nonconductive strips have also been proposed.
[0005] Although input apparatuses having a multilayer material
fabric structure are well suited to the realization of touch
sensors (touch pads) having a high spatial resolution, since a
matrix structure prescribed by the textile structure is read, what
is disadvantageous is that these systems comprise multilayer
textiles and that, at the edge of the input area, in some instances
a large number of connections have to be fed to an electronic
evaluation device. The likewise known possibility of fitting input
keys of a keypad to the textile carrier in particular by embroidery
or sewing methods admittedly enables a high degree of freedom with
regard to the configuration and arrangement of the key devices, but
harbors the disadvantage that this involves a complicated and thus
cost-intensive manufacturing step downstream of the textile
production method.
[0006] Accordingly, it is an object of the invention to specify an
input apparatus which can be integrated into a textile environment
in a simple manner and which is accessible to an industrial scale
manufacturing process. Furthermore, it is an object of the
invention to specify a method for producing such an input
apparatus.
SUMMARY OF THE INVENTION
[0007] According to the invention, an input apparatus comprises
[0008] at least one textile fabric carrier;
[0009] at least one flexible, wire- and/or thread-like electrical
conductor comprising at least one weft and/or warp thread of the
fabric carrier;
[0010] at least one electrically conductive, flexible key device
which is electrically connected to a key connection of the
conductor;
[0011] the conductor being designed for the connection of an
evaluation device.
[0012] The wire- and/or thread-like electrical conductor, which
forms the signal line of the input apparatus or keyboard, is an
integral constituent part of the textile fabric carrier, in which
it comprises at least one electrically conductive weft and/or warp
thread of the fabric carrier. The textile fabric carrier is
understood to be a textile areal structure comprising two thread
systems which cross one another in particular at right angles and
are referred to--as usual--as warp and weft. The warp lies in the
longitudinal direction of the weaving process, while the weft
direction runs transversely with respect to the weaving direction.
The at least one weft and/or warp thread of the fabric carrier,
which imparts conductivity to the electrical conductor, preferably
comprises electrically insulating fibers, in particular synthetic
fibers, which are spun with an in particular electrically
insulated, thin metal wire. As an alternative, it is possible to
form the electrical conductor as a thread-like, thin metal wire
which represents a weft or warp thread of the fabric carrier. This
signal line introduced in the fabric carrier in this way may be
formed directly in the process for producing the fabric carrier, so
that a subsequent cost-intensive additional process does not have
to be performed. Furthermore, a conductor formed in this way also
does not represent an extraneous element in the textile
environment, as is the case with conventional key devices fitted on
textile fabric carriers.
[0013] The conductor is electrically connected to an electrically
conductive, flexible key device. The key device is preferably fixed
directly to the textile fabric carrier, the electrical contact
between key device and conductor being effected by means of an
electrical connection of the key connection to the key device. The
conductor furthermore has an evaluation device, which is designed
for the connection of an evaluation device, in particular an
integrated circuit. The evaluation device may also be connected to
the evaluation connection by interposition of additional
conductors.
[0014] Preferably, the key device comprises a conductive adhesive,
in particular a conductive silicone. Use is preferably made of a
polyorganosiloxane which has been formed in electrically conductive
fashion by addition of electrically conductive constituents, in
particular carbon or carbon black. Such a key device can
advantageously be fitted to the textile fabric carrier by means of
a printing method, in particular a screen printing method.
[0015] Preferably, the key device has a key layer whose layer
thickness is small relative to dimensions of the key layer in the
layer plane and which is areally fixed to the fabric carrier. The
key layer is thus a thin laminar layer which is preferably fitted
to the textile fabric carrier in whole-area fashion. The thickness
of the key layer is small relative to its lateral dimensions. The
key device thus stands out only to a small extent relative to the
textile fabric carrier, so that it does not represent an extraneous
element in the textile environment. Preferably, the conductor has
an electrical insulation, which can be locally removed for
electrical connection to the key device. In this case, the
insulation is preferably removed in a window-like region at or on
which the key device or the key layer bears. The removal step may
be effected in particular by thermal or chemical action, in
particular by means of an etching step or by means of laser
ablation.
[0016] Preferably, the input apparatus comprises a multiplicity of
key devices arranged in particular linearly or in matrix-like
fashion. A matrix-like arrangement in which the key devices adopt a
regular arrangement oriented like a lattice is particularly
preferred.
[0017] In accordance with a preferred embodiment, the conductors
electrically connected to the key devices in each case are
electrically connected at crossover points to contact
redistribution conductors which run essentially perpendicularly
thereto and in each case comprise at least one electrically
conductive weft or warp thread of the fabric carrier. This "contact
redistribution" of the conductors, serving as signal lines for the
key devices, to contact redistribution conductors running
essentially perpendicularly thereto enables the conductors, which
are often spaced apart from one another comparatively far and
irregularly, to be diverted to closely adjacent and regularly
arranged contact redistribution conductors. The large distance
between the conductors which is often necessary in order to form a
textile "keyboard" can thus be adapted to the contact or conductor
period of electronic components, which is typically an order of
magnitude smaller. In this case, the evaluation device is connected
to the contact redistribution conductor. If, by way of example,
electrically conductive warp threads of the textile fabric carrier
are used as conductors, then the contact redistribution conductors
may be formed by weft threads having crossover points with said
warp threads.
[0018] Preferably, the contact redistribution conductors are
arranged in a manner spaced apart uniformly from one another in the
fabric carrier. This regular arrangement of the contact
redistribution conductors simplifies the connection of external
components, in particular external electronic components, to the
contact redistribution conductors. The period of the contact
redistribution conductors may furthermore be adapted to the typical
contact spacings of the evaluation device.
[0019] Preferably, the input apparatus comprises an evaluation
device for detecting an actuation of at least one of the key
devices.
[0020] Preferably, a first group of key devices is designed as
reference key devices and a second group of key devices is designed
as input key devices. An actuation of a key device is present only
when the electrical potential of an input key device changes from
that of a reference key device by means of an external action, e.g.
by means of electrical connection ("short-circuiting") by means of
a finger.
[0021] Preferably, the evaluation device is designed for evaluating
the electrical potential difference or the electrical resistance
between one of the input key devices and at least one of the
reference key devices. Each input key device is preferably
electrically connected directly to the evaluation device, so that
the wiring outlay increases linearly with the number of input key
devices. The reference key devices can be put at an identical
electrical potential, while the electrical potential of the input
key devices is determined relative to the potential of the
reference key devices by means of a threshold value decision unit.
An unavoidable leakage current between the output and reference key
devices can be combated by execution of "refresh" cycles which
regenerate the electrical potential of the input key devices.
[0022] Preferably, the input key devices are connected, by a
conductor arranged in the fabric carrier, serially and with high
impedance to an input connection of the evaluation device and the
reference key devices are connected with low impedance to a
reference connection of the evaluation device. This makes it
possible to evaluate the actuation of an input key device by means
of an analog measurement method, the number of measuring lines
being independent of the number of key devices. The input key
devices connected with a high impedance form a resistive voltage
divider that is designed similarly to the principle of a sliding
potentiometer. If an input key device with a reference key device
is actuated by proximity of a finger, then the finger touching the
key devices represents the "sliding contact" of the sliding
potentiometer. Preferably, the evaluation device is designed for
detecting an actuation of one of the input key devices by
evaluation of the electrical resistance between the input and
reference connections.
[0023] In accordance with a further preferred embodiment, the
evaluation device is designed for outputting a control signal if it
detects an actuation of at least two of the key devices in a
predetermined temporal sequence. Such a "dynamic pattern
recognition" may advantageously be used as a measure against
inadvertent actuation processes of the key devices. Conventionally,
all that are known are reinforcements or stiffenings of the textile
carrier material as protection against folding processes which
might initiate erroneous key actuations. Moreover, input
apparatuses in textile environments have hitherto been positioned
at such locations where these can come into contact with extraneous
objects as little as possible. According to the invention, an
inadvertent initiation of switching processes can be prevented or
minimized in that the evaluation device does not wait for a
discrete activity (for example the actuation of a key device), but
rather for a "dynamic pattern". A switching operation or the
initiation of a control signal is activated only when a
multiplicity of key devices have been actuated in a temporally
predetermined order. By way of example, it is possible to use input
methods similar to the "graffiti alphabet" of conventional
electronic organizers (palm PDA), with the difference that control
commands are interrogated rather than alphanumeric data.
[0024] In accordance with a further particularly preferred
embodiment, the evaluation device is designed for capacitively
detecting an actuation of at least one of the key devices. The
evaluation device thus represents a capacitance sensor which is
designed for detecting changes in the capacitance of the key device
with respect to the environment. By way of example, the capacitance
sensor is designed to detect the change in capacitance of the key
device which concomitantly occurs when an object (e.g. a finger) is
brought close to said device. Key device and evaluation device thus
form a capacitive proximity switch which, in particular, can detect
the contactless actuation of a key device.
[0025] An evaluation device which evaluates not only the
capacitance of the key device with respect to its environment but
also the rate of change of said capacitance with respect to time
(dC/dt) is particularly preferred. This makes it possible to
realize a capacitive proximity switch having a dynamic detection or
switching distance (distance between finger and key device). The
greater the speed at which the object approaches the key device,
the greater the detection distance. Capacitive proximity switches
from EDISEN-electronic GmbH, Lauchhammer, Germany, for example the
proximity switch "Minitaster MT0.2", have proved to be particularly
suitable.
[0026] An essential advantage of a capacitive evaluation device is
the possibility of being able to actuate key devices without
electrical contact being made between finger and key device.
Preferably, the evaluation device is designed in such a way that an
actuation of a key device can be detected without the latter having
to be touched--for example by a finger. In the case of a capacitive
evaluation of key actuations, the key devices can thus be covered
by an electrical insulator. By way of example, the method of
capacitive detection of key actuations also still functions through
relatively thick electrically nonconductive substances covering the
key device(s). As already described above, the entire input
apparatus may be encapsulated for example with plastic (e.g. a
textile hot melt adhesive as is used as standard in the field of
textiles) and thus be insulated, mechanically stabilized and sealed
in machine-washable/cleaning-proof fashion.
[0027] Preferably, the input apparatus comprises an electrical
shielding device, which is designed for electrically shielding at
least one of the key devices from a side of the textile fabric
carrier. The shielding device is designed to prevent electrical or
electromagnetic interference influences from that side of the
textile fabric carrier from which actuation of the key device is
not intended to be effected. If the input apparatus is integrated
into an item of clothing, for example, then the shielding device
prevents an inadvertent actuation of the key device from the body
side of the wearer of the item of clothing. Inadvertent actuations
of the key device which might be initiated by variation of the
distance between item of clothing and body of the wearer can be
avoided by means of a shielding device fitted on the body side.
[0028] Preferably, the shielding device is a thin conductive layer
which is arranged in a manner spaced apart from and running
essentially parallel to the at least one key device. Preferably,
the shielding device has a thin electrically conductive layer,
which is preferably flexible. By way of example, the conductive
layer is a metal-coated plastic film, a textile fabric with a high
proportion of electrically conductive threads, a metal foil or a
textile material printed with conductive ink. The conductive layer
is preferably arranged onto the textile fabric carrier in the
region of the key device(s). Preferably, the shielding device or
the conductive layer is connected to ground.
[0029] According to the invention, a method for producing an input
apparatus, preferably an input apparatus in accordance with the
embodiments described above, comprises the following steps:
[0030] provision of a textile fabric carrier having at least one
flexible, wire- and/or thread-like electrical conductor comprising
at least one weft and/or warp thread of the fabric carrier;
[0031] fitting of an electrically conductive, flexible key device
electrically connected to a key connection of the conductor;
and
[0032] connection of an evaluation device to the conductor.
[0033] Preferably, the key device is fitted by means of a printing
method, in particular a screen printing method. This enables the
simple production--accessible to mass production--of key devices
which are fixed to the textile fabric carrier such that they are
well embedded in the textile environment. Preferably, an electrical
insulation of the conductor is locally removed before the step of
fitting the key device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] The invention is described by way of example below with
reference to accompanying drawings of preferred embodiments, in
which:
[0035] FIG. 1 shows a schematic plan view of an embodiment of an
input apparatus according to the invention, the conductors being
fed to an evaluation device by means of contact redistribution
conductors;
[0036] FIGS. 2a and 2b show a schematic circuit diagram of a
preferred evaluation device and the voltage/time diagram
thereof;
[0037] FIGS. 3a and 3b show a schematic plan view of a further
preferred embodiment of an input apparatus according to the
invention with equivalent circuit diagram;
[0038] FIGS. 4a and 4b show a schematic basic illustration for a
preferred pattern recognition according to the invention; and
[0039] FIG. 5 shows a schematic cross-sectional view of a preferred
embodiment of an input apparatus according to the invention with a
capacitive evaluation device.
DETAILED DESCRIPTION OF THE PREFERRED MODE OF THE INVENTION
[0040] FIG. 1 illustrates a first preferred embodiment of an input
apparatus according to the invention. 10 designates a textile
fabric carrier having a multiplicity of warp threads K and weft
threads S. The warp and weft threads K, S preferably for the most
part comprise electrically insulating synthetic fibers and are thus
insulators. Some selected synthetic fibers thereof have spun-in
thin metal wires, however, which are electrically insulated.
Electrical conductivity is thereby imparted to these selected warp
and weft threads, so that they represent wire- and/or thread-like
electrical conductors 12. The electrically conductive warp and weft
threads K, S, which in each case form a conductor 12 in the
embodiment shown in FIG. 1, are highlighted by a thicker line width
in FIG. 1. It is also possible for a plurality of--in particular
adjacent--electrically conductive warp and weft threads to be
interconnected to form an electrical conductor 12, for redundancy
reasons.
[0041] Key devices 14 (for example made of conductive silicone)
arranged in matrix-like fashion are fixed on the fabric carrier 10,
said key devices in each case being electrically conducted to a
conductor 12 extending in the warp direction. For this purpose, in
the production method, the electrical insulation of the conductors
12 which are connected to the assigned key devices 14 was removed
in a window-like region highlighted in FIG. 1, so that a key layer
of the key device 14 can make direct contact with the thin
conductive metal layer. It is likewise possible, however, in order
to improve the electrical contact between the conductors 12 and the
assigned key devices 14, to fit electrical auxiliary contact
devices to the conductors 12 in the region of the key devices
14.
[0042] The 3.times.3 key arrangement illustrated in FIG. 1
typically has a lateral dimension indicated by the arrow of 2 to 10
cm, preferably 5 cm. Since the key devices 14 preferably comprise a
thin flexible material which is fitted directly onto the fabric
carrier 10 and no external signal lines in addition to the
conductors 12 are required, the result is an input apparatus which
is excellently embedded in the textile environment. As is
illustrated in FIG. 1, the nine conductors 12 extending in the warp
direction are electrically connected at crossover points 16 to
contact redistribution conductors 18 extending in the weft
direction of the fabric carrier 10. By virtue of the targeted
electrical connection of the conductors 12 to the contact
redistribution conductors 18 at the crossover points 16, it is
possible to produce predetermined electrical connections between
the horizontally and vertically running conductive threads. This
makes it possible for the conductors 12, which are spaced apart
irregularly and in part are far away from one another, to be
diverted to more closely adjacent, periodically arranged contact
redistribution conductors 18. This significantly simplifies the
connection of an evaluation device 20.
[0043] If the evaluation device 20 is a capacitive evaluation
device (a capacitance sensor), a shielding device AE is preferably
provided, which prevents an undesirable capacitive actuation of the
key devices 14 from a side of the fabric carrier 10. The shielding
device AE (broken line in FIG. 1) may comprise a conductive layer
which is electrically insulated from the key devices and runs
essentially parallel thereto. It suffices to arrange the shielding
device AE in a region of the input apparatus in which the key
devices 14 are positioned. The evaluation device 20 is connected
via conductors 19, preferably via conductive threads, to a voltage
supply (not illustrated) and actuation inputs of electronic
components (not illustrated).
[0044] FIG. 2 schematically shows a possible preferred evaluation
device 20. In the case of the embodiment shown in FIG. 2(a), the
conductors 12, without contact redistribution conductors 18, are
directly connected to the evaluation device 20. A first group of
the key devices 14 shown in FIG. 2(a) can be put at a defined
electrical potential, for example at ground potential, via the
conductors 12 in order thus to function as reference key devices
14R. A second group of key devices 14 may be directly connected to
the active part of the evaluation electronics and represents
so-called input key devices 14E.
[0045] The input key devices 14E can be charged, under the control
of a periodic signal Vcharge, to the potential Vdd via a PMOS
transistor 22 and a series resistor R. Furthermore, the source
contact of the transistor 22 and the series resistor R are
connected to a buffer 24, which functions as a threshold value
decision unit and has a high-impedance input. The input of the
buffer 24 is at the potential Vkey, while the buffer output is at
the potential Vdata. The buffer converts the analog signal Vkey
into a binary signal Vdata by threshold value decision. If the key
devices 14 are not actuated, i.e. if, in particular, there is no
finger 26 lying on the key devices 14, then the input key devices
14E discharge over time due to unavoidable leakage currents.
However, as long as Vkey does not fall below a predetermined
threshold of the buffer 24, the signal Vdata=1 is present at the
buffer output. If a finger 26 having a certain electrical
conductivity touches the key devices 14 and short-circuits an input
key device 14E with a reference input key device 14R, then said
input key device 14E is discharged more rapidly with respect to
time, so that, within the "refresh" period, illustrated by
vertically running broken lines in FIG. 2(b), the potential Vkey
falls below the set threshold value of the buffer 24. The signal
Vdata at the buffer output thus changes from Vdata=1 to Vdata=0,
thereby indicating an actuation of the input key device 14.
[0046] This temporal profile of the signals Vdata, Vkey and Vcharge
is illustrated schematically in a voltage/time diagram in FIG.
2(b). The periodic "refresh" operations controlled by the signal
Vcharge suffices, in the case of the typical leakage currents of
the otherwise "floating" input key devices 14E, to hold the node
Vkey above the threshold value limit of the buffer 24. As a result
of the short circuit between the key devices 14E and 14R, however,
the input key device 14E discharges so rapidly that the signal
Vdata is set to the value 0.
[0047] In the case of this embodiment variant of a possible
evaluation device as described in connection with FIG. 2, each key
device 14 is directly connected to the evaluation device 20, so
that the wiring and circuitry outlay increases linearly with the
number of key devices. As an alternative, however, the matrix-like
arrangement of the key devices 14 can also be evaluated by means of
an analog measurement method, the number of measuring lines being
independent of the number of key devices. The embodiment variant
illustrated in FIG. 3 has two measuring lines, the connections of
which are designated by Vref and Vm. In this case, the key devices
14 are divided into reference key devices 14R and input key devices
14E as in the embodiment illustrated in FIG. 2.
[0048] The input key devices 14E are electrically
contact-connected, by electrically conductive weft threads S and
the reference key devices 14R are electrically contact-connected by
electrically conductive warp threads K. Through suitable electrical
connections at the crossover points 16 of the electrically
conductive warp and weft threads K, S, a circuit is constructed,
which is illustrated in a simplified equivalent circuit diagram in
FIG. 3(b). In this case, the contact-connection of the conductive
weft and warp threads in the fabric carrier 10 is chosen in such a
way that a resistive voltage divider is formed similarly to the
principle of a sliding potentiometer. In this case, the touching
finger serves as "sliding contact", it being possible to determine
the position of the finger on the matrix of the key devices 14 by
means of a simple resistance measurement between Vref and Vm, since
the input key devices 14e are connected to one another in
series.
[0049] The reference key devices 14R are jointly put at the
potential Vref via electrically conductive warp threads which are
configured with low impedance. The input key devices 14E are
connected to one another in series via electrically conductive weft
threads S with very high impedance. In this case, the resistance R
specified in FIG. 3(b) is the unit resistance of the high-impedance
electrically conductive weft threads S relative to the length of
the spacing of the key devices 14E. The electrical resistance
resulting from the skin conductance of the touching finger is
designated by R.sub.f in FIG. 3(b). The "short-circuit resistance"
between adjacent input and reference key devices 14E, 14R is thus
R.sub.f, where R.sub.f is significantly less than the unit
resistance R. If the finger touches an input key device 14E
together with a reference key device 14R and short-circuits them
with a short-circuit resistance R.sub.f, then the position of this
actuated input key device 14R can be measured and assigned by means
of a resistance measurement between the nodes Vref and Vm.
[0050] FIG. 4 shows schematic sketches of an embodiment of an
evaluation device in which an inadvertent activation or actuation
of a switching operation of a key device can be prevented by means
of a "dynamic pattern recognition". The evaluation device used in
this case is designed for recognizing the temporal order in which
the individual key devices 14 of the keypad are activated. It is
only if the key devices 14 are actuated and recognized in a
predetermined temporal order, i.e. in a specific fixed pattern,
that a corresponding control signal is output and an assigned
function is performed. In this case, each of the key devices 14
illustrated in FIGS. 4(a) and (b) may in each case comprise an
input key device 14E and a reference key device 14R.
[0051] As an example, FIGS. 4(a) and (b) specify a variant of a
dynamic pattern recognition of a 3.times.3 keypad which can be used
for example for controlling a device for audio reproduction. The
arrows in each case represent the sweeping directions of the finger
that are expected by the system for a specific control action, or
actuation sequences of the key matrix. Volume regulation (vol- and
vol+) and skipping forward and back (next, previous) were chosen as
an example in this case. If the evaluation device recognizes other,
non-predetermined input patterns, for example an input pattern
which is represented by the obliquely running arrow in FIG. 4(a), a
control signal is not output. Instead, such non-predetermined
patterns are rejected by the evaluation device and interpreted as
inadvertent actuations.
[0052] FIG. 5 shows a schematic cross-sectional view through a
preferred embodiment of an input apparatus with a capacitive
evaluation device 20. The electrical connection of one of the key
devices 14 to the evaluation device 20 by means of electrical
connections 16 via an electrically conductive thread 28 is shown in
cross section. The conductive thread 28 is insulated by electrical
insulations 30 from the key devices 14 and the shielding device AE,
which represents a ground plate. The capacitive evaluation device
20, i.e. the capacitance sensor, is connected via conductors 19 to
a voltage supply (not illustrated) and external circuits which
process the output signals of the evaluation device 20. For
mechanical and chemical protection, the entire apparatus may be
provided with a waterproof encapsulation 32, a textile upper layer
34 preferably being arranged on the surface thereof. On account of
the capacitive coupling between the finger 26 and the key device
14, there is no need for an electrically conductive connection
between the finger 26 and the key device 14 for the actuation of
the key device 14.
[0053] In addition to the application of the above-described
preferred input apparatuses for data inputting or control in items
of clothing, applications as general touch sensors are also
conceivable, which may be used for example in material coatings in
room decoration, furniture, wall coverings, etc. The keys are
preferably made "invisible" in this case by being produced from a
transparent conductive silicone adhesive. Only the dynamic patterns
to be actuated are represented visibly for example by arrows by
means of a color printing on the fabric carrier. In this case, the
user does not notice the underlying matrix structure of the key
devices.
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